Get set for 2013 corn

The clock is ticking for the start of the 2013 growing season. Here are six answers to commonly asked questions that have surfaced during the winter meeting circuit.

1. How big a yield hit do I take for corn-on-corn?

Corn following corn generally yields an average 10% less compared to corn following another crop, says Emerson Nafziger, University of Illinois (U of I) Extension agronomist.

This consistently occurred again in 2012 across U of I research locations, says Nafziger. It may be that crop rotation is good for root development of corn. Or, it may be that there was a little more water left in the soil tank after a soybean crop. More likely, it's a combination of those and other things that aren't all fully understood, he says.

2. What factors influence herbicide carryover?

Last year's drought has spurred concern that herbicides applied last year may carry over and damage the 2013 crop. Mike Owen and Bob Hartzler, Iowa State University Extension weed specialists, note these factors influence carryover:

» Chemical half-life (persistence in the soil).

» Herbicide rate.

» Application date.

» Soil characteristics (texture, organic matter, pH).

» Rainfall (total amount and distribution throughout year).

» Sensitivity of rotational crop.

» Growing conditions that follow planting the next spring.

The factors influencing carryover the most are the top two: soil persistence and herbicide rate.

3. Which herbicides are most prone to carryover?

Owen and Hartzler have compiled this list of row-crop herbicides with carryover potential. Bear in mind, carryover damage from the following herbicides on this list includes other crops besides corn. Be sure to read the chemical's label for more information.

High risk

» Atrazine (numerous products)

» Chlorimuron (Authority XL, Canopy, Envive, Valor XLT, others)

» Imazaquin (Scepter)

» Simazine (Princep, others)

Moderate to slight risk

» Fomesafen (Reflex, Flexstar, Prefix)

» Clopyralid (Hornet)

» Cloransulam (FirstRate, Hornet, Gauntlet, others)

» Imazethapyr (Pursuit)

Dinitroanilines:

» Pendimethalin (Prowl, others)

» Trifluralin (Treflan, others)

HPPD Inhibitors:

» Isoxaflutole (Balance Flexx)

» Mesotrione (Callisto, Lumax, Lexar)

» Tembotrione (Laudis, Capreno)

» Topramezone (Impact)

N-detection tools

For a look at tools you can use to detect in-season nitrogen needs, go to agriculture.com/crops/corn-high-yield-team.

4. Should I count on carryover if I applied these products?

Not at all. Herbicide carryover worries can be erased by winter and spring precipitation and crop condition.

“You can have herbicide residual that doesn't turn into carryover because of spring weather and the condition of the crop,” says Owen. “The biggest factor is what happens this spring with rainfall, and whether you plant into crops that are under stress. If plants are not stressed, they will be better able to deal with whatever (carryover) herbicide is there.”